Cable spool holder

I recently made this, what I think, quite awesome cable spools for my electronic lab:
http://www.thingiverse.com/thing:1077633

Now I have made a holder to attach to the edge of a shelf/table to get easy access to the prototype cable.

I have attached the spool holder to the shelf where I have my instruments. It is 20cm above the table surface and 60cm back from the edge. The shelf is 30mm thick, and the opening on these brackets is 32mm. I then added two rubber pads on each bracket, to make sure it does not slide of the shelf.